package main

import (
	"fmt"
	"regexp"
)

func main(){
	msg := `{"sn":"da00-0040-c900-0221"}}sdfsdf{asdasd}`

	reg := regexp.MustCompile(`\{{1}[^\{\}]+\}{1}`)
	fmt.Printf("%v\n", string(reg.Find([]byte(msg))))
	//sna := strings.TrimSpace(msg)
	//sn := string(sna[7:26])
	//fmt.Println(sn)
}